My composition turns black before timeline ends.

Hi,

I'm working on a project that's supposed to be 15 seconds long. But I noticed my composition is turning all black before those 15 seconds are up. It happens around the 14th second or so, so there's a whole second of all-black screen, which I don't want.

On the first picture you can see, this is the last moment in which I can see the comp. But you can also see it's supposed to last beyond that.

This is the first instance in which the all black screen problem starts. There's still a couple seconds to go before the 15 seconds are actually up.

I've never had this problem before, and it looks as if everything's set up correctly... is there something I'm missing?

I'm using After Effects 23.4.0.

Thank you.